In many known power stations, an existing device for steam generation and also a steam turbine are also utilized, in, addition to the generation of electrical energy, for generating what may be referred to as distance heat, where partially expanded steam, which still possesses sufficient energy for heating a medium to be heated, is extracted from the steam turbine and supplied as heating medium to one or more heating condensers on the primary side. The medium to be heated, for example water, flows through such heating condensers on the secondary side and is heated by way of the heating medium and supplied to heat consumers.
It is thereby possible to use the energy generation of a power station for the generation both of electrical energy and of distance heat, for example for heating purposes, in which case, as a rule, a high overall efficiency can be achieved.
It must be remembered, in this context, that, as a result of the uncoupling of distance heat, some of the heat energy of the process steam is no longer available for the generation of electrical energy. If, then, the power station is to make available a required quantity of electrical power which is predetermined, for example in the form of a load schedule, by a higher management center, then the regulation of the steam generation of the power station must take into account not only the electrical power requirement, but also that power output fraction which is needed for generating the distance heat and which, as already mentioned, is not available for the generation of electrical energy.
Thus, for example, a regulating device of a steam generator of the power station is acted upon by a higher desired power output value than would be necessary solely for the generation of electrical energy.
That power output fraction which is allocated to the uncoupling of distance heat is designated as what would be called reduced electrical power output which is to be added to the (required) electrical power output of the power station and is to be supplied as a corresponding desired power output value to a power output controller of the power station.
Known methods and devices for determining the abovementioned reduced electrical power output usually make use of empirically determined relations, for example the pressure with which the turbine blades of a high-pressure stage of the steam turbine are acted upon being adopted. Other influences, such as, for example, a varying, in particular higher cooling water temperature or shutdowns of preheaters, may in this case often not be taken into account.
In summary, it can be established that, to determine the reduced electrical power output, operating parameters relating to the steam turbine are adopted to a great extent in the prior art, so that, in particular, a method found for a specific power station for determining the reduced electrical power output cannot readily be transferred to another power station. This is because the corresponding operating parameters of the respective steam turbines depend very closely on the respective type of steam turbine. Therefore relations determined empirically for one steam turbine cannot readily be transferred to another steam turbine.